Cutting tool made by additive manufacturing

ABSTRACT

A cutting tool made by an additive manufacturing process is disclosed. The cutting tool has an exterior surface and an enclosed interior cavity defined by one or more inwardly facing surfaces. The interior cavity may have internal supports such as a lattice or a honeycomb structure. The cutting tool may be an insert, drill or endmill with coolant holes.

RELATED APPLICATION DATA

The present application is a divisional application of U.S. patentapplication Ser. No. 14/710,644 filed May 13, 2015.

FIELD

The present invention relates to the production and design of metalcutting tools.

BACKGROUND

Metal cutting tools are typically made from cemented tungsten carbide oranother suitable material, such as PCD, PcBN, high speed steel and othercerrnets. Cemented tungsten carbide components are made by pressing orextruding blend of WC, Co and possibly other materials into a greenshape. The green shape is then sintered to compact and fuse the powdertogether. Cemented carbides are metal-matrix composites comprisingcarbides of one or more of the transition metals as hard particlesdispersed and cemented in a binder of, for example, cobalt, nickel,and/or iron (or alloys of these metals). In this manner, the hardparticles form a dispersed phase and the binder folios a continuousphase. Cemented carbides offer attractive combinations of strength,toughness, and abrasion/erosion (i.e., wear) resistance for use ascutting tools, including, for example, turning inserts and millinginserts. Among the different possible hard particle combinations,cemented carbides comprising tungsten carbide as the hard particle andcobalt as the binder phase are common choices for cutting tools formetalworking operations on difficult to machine materials, such as, forexample, titanium and titanium alloys, nickel and nickel alloys,superalloys, stainless steels, and ductile iron.

Press and sinter or extrude and sinter technology limits the design ofthe final component to only those geometries that can be pressed orextruded. This can lead to inferior or unnecessary features incorporatedinto cemented carbide components including more material. Oneunnecessary feature is often the use of more material than is needed tomake the component. Cemented tungsten carbide is an expensive material.There is a continuous need to reduce its use without compromisingcutting tool quality or performance.

SUMMARY

In one form thereof, the invention is a cutting tool comprising anexterior surface and an enclosed interior cavity defined by one or moreinwardly facing surfaces. The interior cavity may have internal supportssuch as a lattice or a honeycomb structure.

In another form thereof, the invention is a method of producing acutting tool comprising producing a green cutting tool having aninternal cavity from a starting powder using a binder jetting process,followed by debinding and sintering the cutting tool.

In another form thereof, the invention is a method of producing acutting tool comprising the steps of producing a tool having an internalcavity from a starting powder using a selective laser sintering process.

Tools produced according to this invention may have improved themechanical properties and wear resistance, decreased total weightthrough the elimination of unnecessary material, and decreasedmanufacturing time and costs. In addition, the light weight design ofthe tool will allow for more accurate tool paths in high speedoperations due to the quicker reaction of the machinery. Additionalbenefits of this design include higher quality finished parts increaseddesign flexibility.

These and other embodiments are described in greater detail in thedetailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting insert according to oneembodiment of the present invention.

FIG. 2 is a cross-sectional view of the cutting insert of FIG. 1.

FIG. 3 is a sectional view of a cutting insert according to anotherembodiment of the present invention.

FIG. 4 is a perspective view of drill according to another embodiment ofthe present invention.

FIG. 5 is a cross-sectional view of the drill of FIG. 4.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by referenceto the following detailed description and examples and their previousand following descriptions. Elements, apparatus and methods describedherein, however, are not limited to the specific embodiments presentedin the detailed description and examples. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations will bereadily apparent to those of skill in the art without departing from thespirit and scope of the invention. As used herein, the term cutting toolrefers to a hard component used to remove material from a workpiece.

FIG. 1 illustrates a cutting insert 10 according to one embodiment ofthe present invention. In this embodiment, the cutting insert is in agenerally rectangular form although it could be any desired shapesuitable for metal cutting, for example, another insert style, an endmill or a drill. Moreover, the cutting insert 10 could have additionalgeometric shapes like chip breakers or holes on one or more of itssurfaces. Cutting insert 10 has cutting edges 11 at the intersection ofa rake face 12 and a flank face 13. An exterior surface 14 of thecutting tool 10 comprises the rake face 12, flank face 13 and cuttingedges 11. Cutting inserts of this style are typically indexable andremovably held in a toolholder for a turning or milling operations.

FIG. 2 is a cross-sectional view of the cutting insert 10 of FIG. 1. Thecross-section reveals an interior cavity 15 within the insert 10. Theinterior cavity 15 is defined by one or more inwardly facing surfaces19. A lattice structure 17 is incorporated to improve the mechanicalproperties of the cutting insert 10. The lattice structure 17 may be anysuitable design that maintains the mechanical strength and integrity ofthe tool, for example, one or more interior walls may be added or ahoneycomb structure may be incorporated. As used herein, the term“cavity” refers to an interior space within a tool bounded on all sidesby inwardly facing surfaces.

Referring now to FIG. 3, a cross-sectional view of a cutting insert 20is shown according to another embodiment of the present invention. Thecutting insert 20 has an interior cavity 21 with a supporting latticestructure 22. The cutting insert 20 has a cutting edge 23 at theintersection of a flank face 24 and a rake face 25. Within the rake face25 and adjacent the cutting edge 23 are coolant discharge holes 26extending from the interior cavity 21 to the rake face 25. In thisembodiment, coolant, for example, water or cutting fluid, is deliveredthrough a tool holder (not shown) and into a coolant inlet (not shown)incorporated into the bottom of the cutting insert 20. The bottom of theinsert is the side opposite the rake face 25. Other embodiments may havethe coolant inlet on a flank or rake face.

FIG. 4 and FIG. 5 illustrate a drill 30 according to another embodimentof the present invention. FIG. 5 is a cross-sectional view of a centralportion of the drill 30. The cross section is along a plane intersectingthe longitudinal axis of the drill 30. The drill has a shank 31 at oneend and a cutting tip 32 and cutting edges 33 at an opposite end. Asshown in FIG. 5, the drill 30 has an interior cavity 34 defined by oneor more inwardly facing surfaces 35. Lattice structures 36 providemechanical support for the drill 30.

Cutting tools of the present invention are manufactured by means ofadditive manufacturing, for example, binder jetting, selective lasersintering (SLS), or selective laser melting (SLM). As used herein,“binder jetting” refers to the following method of producing acomponent: selectively spraying liquid binder onto a bed of powder basedon a 3D model of a component, solidifying the binder and powder into across-section, depositing additional powder then binder to form the nextlayer of the object and repeating this process until the green componentis finished. Subsequent to the binder jetting, the component is deboundand sintered. In some embodiments, the cutting tool is hot isostaticpressed (HIP) at a temperature between 2000 and 3000° F. for a timeperiod of between 30 and 500 minutes and a pressure of 10,000 to 30,000psi to obtain a highly dense and reliable structure. Final density ofthe tool is at >95%, for example >99.5%.

Suitable powders include water and gas atomized powder comprising a hardparticle component and a metallic binder component. Turning now tospecific components, the hard particle phase can be present in thesintered cemented carbide article in any amount not inconsistent withthe objectives of the present invention. In some embodiments, forexample, the hard particles phase is present in an amount of at least 70weight percent or at least 80 weight percent of the sintered cementedcarbide article. The hard particle phase can also be present in anamount selected from Table I.

TABLE I Hard Particle Phase Content Wt. % Sintered Cemented CarbideArticle 70-98 80-98 85-96 88-95 89-98 90-97

As described herein, the hard particle phase includes tungsten carbide.In some embodiments, the hard particle phase is formed solely oftungsten carbide. Alternatively, the hard particle phase can furtherinclude carbide, nitride and/or carbonitride of one or more metalsselected from 20 Groups IVB, VB and VIB of the Periodic Table. Forexample, in some embodiments, the hard particle phase comprises at leastone of tantalum carbide, niobium carbide, vanadium carbide, chromiumcarbide, zirconium carbide, hafnium carbide, titanium carbide and solidsolutions thereof in addition to tungsten carbide. Additional metalcarbide, nitride and/or carbonitride can be present in the hard particlephase in any amount not inconsistent with the objectives of the 25present invention. In some embodiments, additional metal carbide,nitride and/or carbonitride is present in an amount of up to 50 wt. % ofthe hard particle phase. For example, additional metal carbide, nitrideand/or carbonitride can be present in an amount of 1-10 wt. % of thehard particle phase. Further, the hard particle phase can generallyexhibit an average grain size less than 30 μm. For example, the hardparticle phase can have an average grain size less than 10 μm, such as0.5-3 μm.

As described herein, the sintered cemented carbide article includes ametallic binder phase comprising one or more alloying additives and thebalance of cobalt, nickel and/or iron. As used herein. “metallic binder”refers to the metallic component which softens during sintering andcements the hard particles together. Metallic binder is part of thepowder blend which is used to create the green component. Generally, themetallic binder phase is present in an amount of 1-30 wt. % of thesintered cemented carbide article. In some embodiments, metallic binderphase is present in an amount selected from Table II.

TABLE II Metallic Binder Phase Content Wt. % Metallic Binder of SinteredCemented Carbide 1-30 2-20 2-12 3-10 4-15 10-30 

Alloying additive of the metallic binder phase comprises one or moremetallic elements, non-metallic elements or solid solutions thereof.Metallic elements suitable for use as alloying additive includetransition metals and aluminum. In some embodiments, transition metalalloying additive is selected from Groups IIIB-VIIm of the PeriodicTable. For example, alloying additive can comprise one or more oftungsten, ruthenium, manganese, copper, rhenium, chromium, osmium andmolybdenum. In some embodiments, metallic alloying additive exhibits 20a hexagonal close-packed (hep) crystalline structure. In otherembodiments, metallic alloying additive has a cubic crystallinestructure, such as face-centered cubic (fcc) or body-centered cubic(bcc). Alloying additive can also include one or more non-metallicelements. Nonmetallic alloying elements can selected from Groups IlIA-VAof the Periodic Table, such as boron, silicon, carbon and/or nitrogen.Generally, alloying additive is present in an amount up to 50 wt. % ofthe metallic binder phase. In some embodiments, for example, alloyingadditive is present in an amount of 10-30 wt. % or 30-50 wt. % of themetallic binder phase.

In some embodiments, a sintered cemented carbide article describedherein further comprises a surface zone of alloy binder enrichmenthaving maximum alloy binder content greater than the alloy bindercontent in the bulk of the sintered article. The zone of binderenrichment can extend inwardly from the sintered article surface. Insome embodiments, alloy binder of the enrichment zone is stratified,exhibiting distinct layers of alloy binder. In other embodiments, thealloy binder is non-stratified. The sintered cemented carbide articlecan exhibit a surface zone of alloy binder enrichment on one or multiplesurfaces.

Nonlimiting examples of binders that may be used with the inventivesuspensions include binders such as ethylene glycol monomethyl ether,polyethylene glycol, polyvinyl alcohol (PVA), polyvinyl butyral (PVB),polyvinylpyrrolidone (PVP) and waxes. The concentration of the binder ina may be from about 5 to about 10 weight percent binder. Tools can madewith an ExOne binder jet printer utilizing a suitable binder and powdercombination as described above.

In some embodiments, cutting tools described herein are coated with oneor more refractory materials by PVD and/or CVD. In some embodiments, therefractory coating comprises one or more metallic elements selected fromaluminum and metallic elements of Groups IVB, VB and VIB of the PeriodicTable and one or more non-metallic elements selected from Groups IIIA,IVA, VA and VIA of the Periodic Table. For example, the refractorycoating can comprise one or more carbides, nitrides, carbonitrides,oxides or borides of one or more metallic elements selected fromaluminum and Groups IVB, VB and VIB of the Periodic Table. Additionally,the coating can be single-layer or multi-layer.

Further, cutting tools described herein can be subjected to one or moretreatments such as polishing, blasting and/or etching. The surfacetreated sintered cemented carbide articles can remain in the uncoatedstate or a refractory coating described herein can be applied to thetreated surfaces. Moreover, one or more layers of the refractory coatingcan be subjected a post-coat treatment such as polishing and/orblasting.

Additive manufacturing techniques enable a wholly enclosed cavity to bedesigned into a cutting tool. The cavity may additionally have latticeor other supports designed into the tool to increase its strength. Priorart press and sinter techniques are not capable of producing a whollyenclosed interior cavity. An enclosed cavity with lattice supportsallows for design of the cutting tool with minimal material use whilemaintaining mechanical strength of the tool.

Various embodiments of the invention have been described in fulfillmentof the various objects of the invention. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations thereof willbe readily apparent to those skilled in the art without departing fromthe spirit and scope of the invention.

That which is claimed is:
 1. A method of making a cutting tool comprising: forming a green cutting tool from a powder composition via a binder jetting process, the green cutting tool comprising an exterior surface and an enclosed interior cavity defined by inwardly facing surfaces, wherein one or more lattice structures are formed within the interior cavity and subsequently enclosed by the inwardly facing surfaces during the binder jetting process, and the interior cavity is supported by the one or more lattice structures; and sintering the green article to provide a sintered cutting tool having final density greater than 95% theoretical density, wherein the powder composition comprises a sintered hard particle component comprising a metallic binder component.
 2. The method of claim 1, wherein the sintered hard particle component is present in an amount of at least 70 weight percent of the powder composition.
 3. The method of claim 1, wherein the sintered hard particle component comprises tungsten carbide.
 4. The method of claim 3, wherein the sintered hard particle component further comprises a carbide, nitride or carbonitride of one or more metals selected from Groups IVB, VB and VIB of the Periodic Table.
 5. The method of claim 1, wherein the metallic binder component is present in an amount of 10 to 30 weight percent of the powder composition.
 6. The method of claim 1, wherein the metallic binder component comprises cobalt, nickel or iron or an alloy thereof.
 7. The method of claim 6, wherein the metallic binder component further comprises an alloying additive selected from the group consisting of ruthenium, rhenium and molybdenum.
 8. The method of claim 6, wherein the metallic binder component further comprises a metallic alloying additive having a hexagonal close packed crystalline structure.
 9. The method of claim 1, wherein the sintered hard particle component has an average grain size less than 30 μm.
 10. The method of claim 1, wherein the sintered hard particle component has an average grain size less than 10 μm.
 11. The method of claim 1, wherein the sintered hard particle component has an average grain size of 0.5-3 μm.
 12. The method of claim 1 further comprising hot isostatic pressing the sintered cutting tool.
 13. The method of claim 12, wherein the sintered cutting tool is hot isostatic pressed at a pressure of 10,000 to 30,000 psi.
 14. The method of claim 1, wherein the cutting tool is a cutting insert.
 15. The method of claim 1, wherein the cutting tool is selected from the group consisting of a drill, reamer and endmill.
 16. The method of claim 15, wherein the cavity and lattice structures are located in a working end of the drill, reamer and endmill.
 17. The method of claim 1 further comprising coating the sintered cutting tool with a refractory material, the refractory material comprising one or more metallic elements selected from aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements selected from Groups IIIA, IVA, VA and VIA of the Periodic Table.
 18. The method of claim 17, wherein the coating is deposited by physical vapor deposition.
 19. The method of claim 17, wherein the coating is deposited by chemical vapor deposition.
 20. The method of claim 1, wherein the sintered hard particle component consists essentially of sintered cemented carbide powder. 